Crest Factor Reduction (“CFR”) is used to limit the dynamic range of signals being transmitted in wireless communications and other applications. Multiuser and multi-carrier signals may have a high peak-to-average ratio (“PAR”). A high PAR places a high demand on data converters and may limit the efficiency of operation of a power amplifiers (“PAs”) used in cellular base stations. Reducing PAR is therefore beneficial in increasing PA efficiency by allowing higher average power to be transmitted before saturation occurs.
Along those lines, peak-cancellation-CFR (“PC-CFR”) cores have been used to process control and data through a transmitter. Such PC-CFR cores are described in additional detail in “LogiCORE IP Peak Cancellation Crest Factor Reduction”, by Xilinx, Inc., XMP039, published Dec. 2, 2009 (ver. 2.0). As indicated in this document, resource requirements and performance may be substantially dependent on data rate and the number of cancellation pulse generators used in an implementation. Along those lines, in a conventional PC-CFR implementation, such PC-CFR may run at 3×-5× of an up-sampled signal for accurate peak detection and cancellation. Thus, for example for an 80 MHz signal bandwidth with 4× sampling, processing may have to be at least at 4×80 MHz, or a 320 MHz sampling rate, with cancellation pulse generators operating at such sampling frequency. This does not take into account any margin for error, namely any guard bands, which may increase such sampling rate.
Accordingly, it would be desirable to provide cancellation pulse generation with a lower sampling frequency than 3× of a bandwidth frequency.